Add new exception ExtraItemsError

[surabujin]

This allow caller to analise errors from extra fields programmatically.
Without this error type to know which fields treated as "extra" caller
must parse error string.

[tseaver]

You can fix the coverage failure by moving the _('Unrecognize items') into the function signature itself. E.g.:

class ExtraItemsError(Invalid):
    def __init__(self, node, extras, msg=_('Unrecognized items')):
        super(ExtraItemsError, self).__init__(node, msg)
        self.extras = extras

[surabujin]

In this case it will be evaluated on module import time. Is it not too early? I think many program make message translation configuration on more later stage.

[tseaver]

LGTM, assuming the coverage failure is fixed.

[mmerickel]

This needs docs updated and a changelog entry.

For example

colander/colander/__init__.py

Line 553 in f7dabb5

- ``raise`` will cause a :exc:`colander.Invalid` exception to

. However it needs to be rendered into the api docs as well.

Also please add your name to CONTRIBUTORS.txt.

[surabujin]

Is it ok now?

[leplatrem]

nit: Unknown looks more appropriate than Unrecognized

[leplatrem]

Great and useful feature!

I had troubles understanding the name of the exception. Couldn't we find something with Unknown in the name? Like UnknownKeyErrror?

[surabujin]

As for me, UnknownKeyError is too common. But I don't insist on my variant, so it up to community.

[tisdall]

In case anyone else is thinking the same thing I first thought...

When I first saw this I thought "what's the point?". If you get random keys you didn't expect then there's not really any way to recover from that so just throw the exception and be done with it. And while that's still true, what @surabujin is trying to do is make the exception into a format that can be transformed into errors that conform to some convention in other libraries. Specifically, he's trying to throw Cornice JSON errors that outline more specifically where an error occurred in the REST service (if I'm understanding his PR to Cornice properly).

[surabujin]

@tisdall yep - you understand everything right. I will need some more changes to colander, if this and cornice PR will be approved.

[lmctv]

Some bikeshedding, since another conflict-resolving merge is needed... why not UnexpectedItemError ?

[mmerickel]

I'm going to rename this to UnknownItemsError as it maps better to the unknown='raise' option to Mapping(). Similarly instead of error.extras it'll be error.unknown_items. Otherwise LGTM.

[mmerickel]

Changed my mind for the last time. Error will be UnsupportedFields with a fields attribute.

[lmctv]

+1 for UnsupportedFields!